We've got an adult rat with incredibly soft fur like a kitten's. I wondered what coat type she could have. She's definitely an adult at 15 months and was 8 months when we got her. The difference is noticeable to her cage-mate who has the same coat type as all my other female rats have had (I've only ever had one rex and he was a buck).

I wouldn't describe Marshmallow's fur as satin or velvet. It's just very soft and fluffy. As I say, kitten-like is the best way to describe it. I don't think you could tell from a pic hence I'm not posting one. She's a dumbo red-eyed himmy if that's any help.